B-cell receptor complex binding proteins containing t-cell epitopes

ABSTRACT

The present invention relates to a polypeptide comprising a) a binding peptide binding to at least one protein selected from the group consisting of CD22, CD19, CD20, and CD21, and b) an immunogenic peptide comprising at least one T-cell epitope for use in vaccination of a subject against B-cell hyperproliferation or for use in the modulation of the immune response in a subject. The present invention further relates to a polynucleotide and a vector encoding said polypeptide and a host cell comprising the same. It also relates to a method for the stimulation of antigen-specific T-cells, comprising a) contacting antigen presenting cells (APC) with a polypeptide, the polynucleotide, or the vector of the invention, b) contacting said APC with T-cells, and c) thereby stimulating antigen-specific T-cells specific for said at least one T-cell epitope; to a method for immunizing a subject against B-cell hyperproliferation, to a method for immunizing a subject against an infectious agent, and to a method for inducing tolerance in a subject.

The present invention relates to a polypeptide comprising a) a bindingpeptide binding to at least one protein selected from the groupconsisting of CD22, CD19, CD20, and CD21, and b) an immunogenic peptidecomprising at least one T-cell epitope for use in vaccination of asubject against B-cell hyperproliferation or for use in the modulationof the immune response in a subject. The present invention furtherrelates to a polynucleotide and a vector encoding said polypeptide and ahost cell comprising the same. It also relates to a method for thestimulation of antigen-specific T-cells, comprising a) contactingantigen presenting cells (APC) with a polypeptide, the polynucleotide,or the vector of the invention, b) contacting said APC with T-cells, andc) thereby stimulating antigen-specific T-cells specific for said atleast one T-cell epitope; to a method for immunizing a subject againstB-cell hyperproliferation, to a method for immunizing a subject againstan infectious agent, and to a method for inducing tolerance in asubject.

By immunization, a subject's immune system becomes fortified against anantigen. Especially the adaptive immune system, i.e. the part of theimmune system that confers the capability of an individual's immunesystem to recognize, remember, and cope with potential pathogens, hasbeen of strong medical interest (Kaech et al. (2002), Nature ReviewsImmunology 2(4):251-62; Pulendran and Ahmed (2006), Cell 124(4):849-63).On the one hand, it has been extensively exploited in vaccination toconfer immunity to otherwise potentially deadly disease. It has alsobeen used with variable success to eliminate cancer cells throughrecognition of tumor antigens. On the other hand, attenuation of theadaptive immune system is of interest in diseases where a strong immuneresponse is inappropriate, like e.g. in allergy, asthma, or autoimmunedisease.

Despite the overall success of vaccination, there are severaldisease-causing agents, like viruses (e.g. human immunodeficiency virus,Epstein-Barr virus), Bacteria (e.g. Staphylococcus spec., Borelliaspec.), eukaryotic pathogens (e.g. Trypanosoma spec.), but also cancercells, that have escaped from becoming amenable for vaccination. Thereasons for this are complex and depend to a large extent on the natureof the specific agent, but also on the physiological state of theindividual to be vaccinated. For some disease-causing agents, methods tofortify the immune response during vaccination, like the use ofvirus-like particles instead of soluble antigen, inclusion of adjuvants,use of live vaccines, and the like, have been devised. It has also beenproposed to boost the immune response by delivering suitable epitopes,which are typically peptides, to the professional antigen presentingcells, i. e. macrophages, dendritic cells, and B-cells.

The principal role of B-cells in the immune system is the production ofantigen-specific antibodies upon their activation. Activation requiresthat the B-cell-receptor (BCR) on the surface of the B-cell becomesbound to its cognate antigen. This activation of the BCR leads toactivation of the B-cell, which undergoes maturation and clonalexpansion, after which part of the cells produced this way becomesplasma cells producing antibodies specific for said antigen. The BCRmediates this activation; it consists of a membrane-bound antibodymolecule specifically able to recognize one antigenic structure, alongwith several co-receptors, including CD21 and CD19. Two other surfacemolecules of the B-cell, CD20 and CD22, are known to—at leasttemporarily—interact with the BCR and act as positive and negativeregulators, respectively. Thus, they can be considered as being membersof the BCR complex (BCRC) in a wider sense. Common to all four moleculesis their internalization into cytoplasmic vesicles and their fusion withthe endosome upon ligand binding.

Another important branch of the adaptive immune system areepitope-specific T-cells. In humans, these cells have a T-cell-receptoron their surface, the recognition domain of which is specific for adefined complex between an antigenic peptide (T-cell epitope) and amajor histocompatibility complex (MHC) protein. If the T-cell-receptoris engaged in a cognate interaction, the T-cell becomes activated,multiplies, and performs its activatory or inhibitory task in the immuneresponse.

The MHC molecules come in two forms: MHC class I are expressed on thesurface of every human cell and present, essentially randomly, peptidesderived from proteins present in the cell's cytosol; they, thus, give acontinuous overview of the protein repertoire of the cell and allow forrecognition of non-normal protein expression, e.g. during viralinfection of the cell or in carcinogenesis. In order to recognize MHCclass I molecule—peptide complexes, the T-cell receptor requires the CD8surface protein as a co-receptor. There is thus a subclass of T-cellsexpressing the CD8 co-receptor, named CD8+-T-cells; their main but notexclusive function is to eliminate body cells presenting peptides thatindicate potential pathogenic processes in said cell, e.g. virusinfection, which is why they are also called cytotoxic T-cells.

MHC class II are expressed only on professional antigen presenting cells(APCs). On these, peptides are presented that are derived from proteinsthat were ingested by the APCs, mainly by endocytosis. Recognition ofMHC class II requires the coreceptor CD4, which is expressed only on thesurface of CD4+ T-cells. The primary role of these T-cells, also calledT-helper cells, is the activation of CD8+-T-cells, macrophages, andB-cells. Delivery of suitable epitopes to APCs thus leads topresentation of these epitopes via MHC class II to helper T-cells, whichin turn activates these T-cells and leads to the activation of the otherbranches of the immune system. Importantly, experimental evidence existsthat co-engagement of the CD19/CD21 complex results in more rapid andefficient production of antigenic peptide/class II complexes as comparedwith engagement of the B cell receptor alone by the antigen (Fearon D Tet al. (2000), Annu Rev Immunol 18:393-422).

Methods used so far to deliver epitopes to APCs have included incubationof APCs with soluble antigens, infection with live attenuatedmicro-organisms, infection with viral vectors derived from vaccinia orother viruses, and injection of DNA vaccines. Results with these methodswere, however, not satisfactory in all cases.

Also, depletion or inhibition of APCs, especially B-cells, has been usedto attenuate the adaptive immune response in diseases where there is anoverreaction (e.g. allergy) or misdirected reaction (e.g. autoimmunedisease). However, with the current treatments available, these diseasesin many cases cannot be treated satisfactorily.

There is thus still an existing need for improved vaccines and otherimmune modulators. The technical problem underlying the invention can beseen as the provision of means and methods which allow for improvedvaccination and immune modulation. The technical problem is solved bythe embodiments characterized in the claims and herein below.

Therefore, the present invention relates to a polypeptide comprising a)a binding peptide binding to at least one protein selected from thegroup consisting of CD21, CD19 CD20, and CD22, and b) an immunogenicpeptide comprising at least one T-cell epitope for the use in modulationof the immune response in a subject.

As used in this specification, the term “polypeptide” relates to anychemical molecule comprising at least a binding peptide and at least oneimmunogenic peptide as specified herein below. It is to be understoodthat the chemical linkage between the binding peptide and theimmunogenic peptide(s) need not necessarily be a peptide bond. It isalso envisaged by the present invention that the chemical bond betweenthe binding peptide and the immunogenic peptide(s) is an ester bond, adisulfide bond, or any other suitable covalent chemical bond known tothe skilled artisan. Also envisaged are non-covalent bonds with adissociation constant so low that the immunogenic peptide(s) will onlydissociate to a negligible extent from the binding peptide. Preferably,the dissociation constant for said non-covalent bond is less than 10⁻⁵mol/l (as it is the case with the Strep-Tag: Strep-Tactin binding), lessthan 10⁻⁶ mol/l (as it is the case in the Strep-TagII: Strep-Tactinbinding), less than 10⁻⁸ mol/l, less than 10⁻¹⁰ mol/l, or less than10⁻¹² mol/l (as it is the case for the Streptavidin: Biotin binding).Methods of determining dissociation constants are well known to theskilled artisan and include, e.g., spectroscopic titration methods,surface plasmon resonance measurements, equilibrium dialysis and thelike. Preferably, the chemical linkage between the binding peptide andthe immunogenic peptide(s) is a peptide bond, i.e. the polypeptide is afusion polypeptide comprising or consisting of the binding peptide andthe immunogenic peptide of the present invention. Preferably, thepolypeptide does not comprise one or more peptide sequences known toinhibit antigen presentation. Moreover, preferably, the polypeptide doesnot comprise genetic material, i.e. polynucleotides. In a preferredembodiment, the polypeptide consists of the components as describedherein.

The term “binding peptide” as used herein relates to any peptide bindingto at least one protein of the B-cell receptor complex (BCRC), whereinthe proteins of the BCRC, preferably, are CD21, CD19 CD20, and CD22,with an affinity that permits internalization of said binding peptide bya B-cell. Preferably, the dissociation constant for the binding of saidbinding peptide to said protein of the B-cell receptor complex of lessthan 10⁻⁵ mol/l, less than 10⁻⁶ mol/l, less than 10⁻⁷ mol/l, less than10⁻⁸ mol/l, or less than 10⁻⁹ mol/l. Preferably, the binding peptide isa peptide from the N-terminus of the Epstein-Barr virus (EBV, alsoreferred to as Human Herpesvius 4) glycoprotein gp350/220 (gp350, gene:SEQ ID NO: 1, Genbank Acc No: NC_(—)009334.1 G1:139424470, proteinproduct SEQ ID NO: 2, Genbank Acc No: YP_(—)001129462.1 GI:139424497),more preferably the binding peptide comprises the first 470 amino acidsof the EBV gp350 or another CD21-binding peptide of EBV gp350. Inanother preferred embodiment, the binding peptide is an antibody bindingto at least one of the B-cell receptor complex proteins (BCRC proteins)specified above. Preferred binding peptides are:

-   -   a mouse anti-human CD21 antibody, comprising a heavy chain (SEQ        ID NO: 25) encoded by

Genbank Acc No: GQ850526.1 GI: 282721923, SEQ ID No. 13, and comprisinga light chain (SEQ ID NO: 26) encoded by Genbank Acc No: GQ850527.1 GI:282721925, SEQ ID No. 14;

-   -   a mouse anti-human CD19 antibody, comprising a heavy chain        variable fragment encoded by Genbank Acc No: X99230.1 GI:        1435158, SEQ ID NO: 37 (e.g. the heavy chain of SEQ ID NO: 27,        encoded by SEQ ID No. 15), and comprising a light chain variable        fragment encoded by Genbank Acc No: X99232.1 GI: 1435165, SEQ ID        NO: 38 (e.g. the light chain of SEQ ID NO: 28, encoded by SEQ ID        No. 16);    -   a mouse anti-human CD22 antibody, comprising a heavy chain        variable fragment encoded by Genbank Ace No: 577347 GI: 998423,        SEQ ID NO: 39 (e.g. the heavy chain of SEQ ID NO: 29, encoded by        SEQ ID No. 17) and comprising a light chain variable fragment        encoded by Genbank Ace No: S77340 GI: 998421, SEQ ID NO: 40        (e.g. the light chain of SEQ ID NO: 30, encoded by SEQ ID No.        18);    -   a mouse anti-human CD20 antibody, comprising a heavy chain        variable fragment encoded by Genbank Acc No: AY058907.1 GI:        16902039, SEQ ID NO:41 (e.g. the heavy chain of SEQ ID NO: 31        encoded by SEQ ID NO: 19) and comprising a light chain variable        fragment encoded by Genbank Acc No: AY058906.1 GI: 16902037, SEQ        ID NO: 42 (e.g. the light chain of SEQ ID NO: 32 encoded by SEQ        ID NO: 20).

As used herein, the term “antibody” relates to a soluble immunoglobulinfrom any of the classes IgA, IgD, IgE, IgG, or IgM. Antibodies againstthe BCRC proteins can be prepared by well known methods using a purifiedprotein or a suitable fragment derived therefrom as an antigen. Afragment which is suitable as an antigen may be identified byantigenicity determining algorithms well known in the art. Suchfragments may be obtained either from the polypeptide of the inventionby proteolytic digestion or may be a synthetic peptide. Preferably, thepeptide suitable as an antigen is located at the exterior of the B-cellin its natural context. Preferably, the antibody of the presentinvention is a monoclonal antibody, a polyclonal antibody, a human orhumanized antibody or primatized, chimerized or fragment thereof Morepreferably, the antibody is a single chain antibody. Also comprised asantibodies of the present invention are a bispecific antibody, asynthetic antibody, an antibody fragment, such as Fab, Fv or scFvfragments etc., or a chemically modified derivative of any of these.Preferably, the antibody of the present invention shall specificallybind (i.e. does not cross react with other polypeptides or peptides) tothe BCRC protein of the invention. Specific binding can be tested byvarious well known techniques. Antibodies or fragments thereof can beobtained by using methods which are described, e.g., in Harlow and Lane“Antibodies, A Laboratory Manual”, CSH Press, Cold Spring Harbor, 1988.Monoclonal antibodies can be prepared by the techniques originallydescribed in Köhler and Milstein (1975), Nature 256, 495; and Galfré(1981), Meth. Enzymol. 73, 3, which comprise the fusion of mouse myelomacells to spleen cells derived from immunized mammals.

Preferably, the binding peptide is contiguous in amino acid sequencewith the immunogenic peptide, i.e. the binding peptide and theimmunogenic peptide form a fusion polypeptide. More preferably, thefusion polypeptide comprises an immunogenic peptide fused to a heavychain or a light chain of an antibody. Most preferably, the fusionpolypeptide comprises an immunogenic peptide from EBV EBNA3C fused to aheavy chain of a mouse antibody binding to a BCRC protein, e.g. thefusion protein of SEQ ID NO: 33 (anti-CD21 heavy chain fused toEBNA3C-5H11 epitope, encoded by SEQ ID NO: 21), SEQ ID NO: 34 (anti-CD19heavy chain fused to EBNA3C-5H11 epitope, encoded by SEQ ID NO: 22), SEQID NO: 35 (anti-CD22 heavy chain fused to EBNA3C-5H11 epitope, encodedby SEQ ID NO: 23), or SEQ ID NO: 36 (anti-CD20 heavy chain fused toEBNA3C-5H11 epitope, encoded by SEQ ID NO: 24). It is, however, alsoenvisaged by the present invention that, preferably, the binding peptideis contiguous in amino acid sequence with an adapter molecule bindingthe immunogenic peptide as described herein above. It is clear for theperson skilled in the art that in such case the immunogenic peptidepreferably comprises an adapter molecule suited to bind, covalently ornon-covalently, to the adapter molecule fused to the binding peptide,e.g., preferably, the binding peptide is fused to a Strep-Tag and theimmunogenic peptide is fused to Strep-Tactin.

The term “CD21” as used herein relates to the human cluster ofdifferentiation protein 21, also known as complement receptor 2 (CR2)(Transcript variant 1: SEQ ID NO: 3, Genbank Acc No: NM_(—)001006658.2GI:260099695, protein product SEQ ID NO: 4, Genbank Acc No:NP_(—)001006659.1 GI:54792123; Transcript variant 2: SEQ ID NO: 5,Genbank Acc. NM_(—)001877.4 GI:260099700, protein product SEQ ID NO: 6,Genbank Acc No: NP_(—)001868.2 GI:42544177). The term “CD19” relates tothe human cluster of differentiation protein 19 (transcript SEQ ID NO:7, Genbank Ace No: NM_(—)001178098.1 GI:296010920; protein product SEQID NO: 8, Genbank Ace No: NP_(—)001171569.1 GI:296010921). The term“CD20” relates to the human cluster of differentiation protein 20(transcript SEQ ID NO: 9, Genbank Acc No: NM_(—)152866.2 GI:68348720;protein product SEQ ID NO: 10, Genbank Ace No: NP 068769.2 GI:23110987).The term “CD22” relates to the human cluster of differentiation protein22 (Transcript SEQ ID NO: 11, Genbank Acc No: NM_(—)001771.3GI:297374826, protein product SEQ ID NO: 12, Genbank Ace No:NP_(—)001762.2 GI:157168355). It is envisaged by the present inventionthat the terms for the BCRC proteins CD21, CD19, CD 20, and CD22 shallalso include homologs, orthologs, and naturally occurring variants (e.g.variants translated from splice variants) of the respective proteins inmammals.

The term “immunogenic peptide” as used herein relates to a peptidecomprising at least one T-cell epitope. A T-cell epitope, as is known tothe one skilled in the art, is a contiguous sequence of amino acidscomprised in a peptide, which can be bound to a major histocompatibilitycomplex (MHC) class I or class II molecule to be presented on thesurface of a cell (MHC-I) or of a professional antigen presenting cell(MHC-II). The skilled artisan knows how to predict immunogenic peptidespresented on MHC-I or MHC-II (Nielsen et al., (2004), Bioinformatics, 20(9), 1388-1397), Bordner (2010), PLoS ONE 5(12): e14383) and how toevaluate binding of specific peptides (e.g. Bernardeau et al., (2011), JImmunol Methods, 371(1-2):97-105). Preferably, the T-cell epitope is anMHC-II epitope. Preferably, the T-cell epitope is an epitope derivedfrom a tumor antigen, i.e. an amino acid sequence comprised in a proteinexpressed essentially only in or on a tumor cell. In a preferredembodiment, the T-cell epitope is an epitope derived from a B-celllymphoma tumor antigen. More preferably, the T-cell epitope is anepitope derived from a latent gene product of EBV. Most preferably, theT-cell epitope is an amino acid sequence comprised in one of the latentgene products of EBV known or suspected to contribute to celltransformation, i.e. one of the EBV EBNA2, LMP1, EBNA3A, -B and -Cproteins (Long et al. (2011), Curr Opin Immunol 23(2):258-64). In apreferred embodiment, the T-cell epitope is a strong T-cell epitope asdetailed herein below.

The term “modulation of the immune response”, as used in thisspecification, relates to inducing a change in the response of asubject's adaptive immune system by applying a polypeptide of thepresent invention. The modulation may be an activation, i.e. lead to anenhanced response to the T-cell epitope(s); or the modulation may be arepression, i.e. lead to a decreased response, e.g. tolerance, to theT-cell epitope(s). The modulation of immune response, preferably,effects amelioration of a disorder or disease or of symptoms accompaniedtherewith to a significant extent in a subject, or, also preferably,modulation of immune response effects retaining health with respect todisease or disorder for a certain period of time in a subject. Saideffect of modulation of immune response as used herein also includes anentire restoration of the health with respect to the disease ordisorder. It is to be understood that modulation of immune response asused in accordance with the present invention may not be effective inall subjects to be treated. However, the term shall require that astatistically significant portion of subjects suffering from a diseaseor disorder can be successfully treated or that a statisticallysignificant portion of subjects of a cohort or population areeffectively prevented from suffering from a disease or disorder or itsaccompanying symptoms. Whether a portion is statistically significantcan be determined without further ado by the person skilled in the artusing various well known statistic evaluation tools, e.g., determinationof confidence intervals, p-value determination, Student's t-test,Mann-Whitney test etc. Preferred confidence intervals are at least 90%,at least 95%, at least 97%, at least 98% or at least 99%. The p-valuesare, preferably, 0.1, 0.05, 0.01, 0.005, or 0.0001. Preferably, themodulation of immune response shall be effective for at least 60%, atleast 70%, at least 80%, or at least 90% of the subjects of a givencohort or population. Preferably, the modulation of the immune responseis a vaccination against an infectious agent, vaccination against B-cellhyperproliferation, or induction of tolerance to an antigen causingautoimmune disease.

The term “infectious agent”, as used herein, preferably relates to amicroorganism causing disease in a subject. Preferably, the infectiousagent is a bacterium, an eukaryotic infectious agent, e.g. a Plasmodiumspp., more preferably a virus, e.g. a Hepatitis virus or HumanImmunodeficiency Virus (HIV). In a preferred embodiment, the infectiousagent is an agent causing chronic disease. More preferably, theinfectious agent is an agent causing chronic and/or persistinginfection. Still more preferably, the infectious agent is an agentcausing chronic and/or persisting infection by modulation of least oneantigenic determinant of said infectious agent. Most preferably, atleast five, at least ten, at least fifteen, at least twenty modulatedforms of the aforesaid antigenic determinants are known, preferablyknown to occur in a body of a subject. In a further preferredembodiment, the aforesaid modulated antigenic determinant is apolypeptide.

As used herein, the term “B-cell hyperproliferation” relates to anincreased proliferation of B-cells as compared to normal. Preferably,B-cell hyperproliferation is EBV-associated diseases includinginfectious mononucleosis or post-transplant lymphoproliferative disorder(PTLD), or B-cell lymphoma.

As used herein, the term “inducing tolerance” relates to inducing adecreased response to an immunogenic peptide in a subject. Preferably,tolerance is induced in subjects suffering from or being at risk tosuffer from an autoimmune disease. Also preferably, tolerance is inducedto immunogenic peptides, the immune response against which is known toaggravate said autoimmune disease. Preferred autoimmune diseases areMultiple Sclerosis, Rheumatoid Arthritis, or Autoimmune Thyroiditis, orother autoimmune diseases for which immunoreactive T cell epitopes havebeen identified.

In further preferred embodiments, the present invention relates to apool of polypeptides as defined herein below, a pool of polynucleotidesas defined herein below, and to a pool of vectors as defined hereinbelow.

The kind of modulation achieved by application of the polypeptide of thepresent invention depends on several factors: The type of APC has amarked influence on the outcome of the immune response; resting Blymphocytes typically induce tolerance whereas dendritic cells andactivated B blasts such as immunoblasts induce activation. Therefore,targeting of activated B cells such as B cell lymphoma leads to T cellrecognition and eventually to their elimination. In contrast targetingof resting B cells with an auto antigen leads to its tolerance. The doseof delivered antigens also plays an important role; very low and highamounts of antigens tend to induce tolerance, intermediate amounts leadto T cell activation. Furthermore, the immunostimulatory effects ofantibodies or polypeptides that target CD19, CD21 or CD20 or in contrastthe B immunosuppressive effects of antibodies directed towards CD22 willalso influence the outcome of the antigen delivery.

The term “subject” relates to an animal, preferably a mammalianorganism, with the capacity to generate an immune response to moleculesforeign to the organism and comprising at least one BCRC protein. Morepreferably, the subject is a cattle, pig, sheep, horse, cat dog, mouse,or rat, most preferably a human being.

The definitions made above apply mutatis mutandis to the following:

The present invention also relates to a polynucleotide encoding abinding peptide covalently connected to the immunogenic peptide or withan adapter binding the immunogenic peptide.

The term “polynucleotide” as used in accordance with the presentinvention, preferably, relates to a polynucleotide comprising a nucleicacid sequence which encodes a fusion polypeptide comprising a bindingpeptide and an immunogenic peptide as specified herein above, or whichencodes a fusion polypeptide comprising a binding peptide and an adapterpeptide as specified herein above. Suitable assays for measuring theactivities of the binding peptide and the immunogenic peptide mentionedbefore are described in the accompanying examples or in (Adhikary et al.(2006), J. Exp. Med. 203(4):995-1006; Busse et al. (2010), J. Virology84(2):1139-47; Gurer et al. (2008), Blood 112(4):1231-9). Apolynucleotide encoding a fusion polypeptide comprising theaforementioned peptides has been obtained in accordance with the presentinvention by cloning immunogenic peptides into polypeptides specificallybinding proteins of the BCRC using well known techniques.

Thus, the polynucleotide, preferably, comprises the nucleic acidsequence shown in SEQ ID NO: 21-24 encoding the polypeptide having anamino acid sequence as shown in SEQ ID NO: 33-36. It is to be understoodthat a polypeptide having an amino acid sequence as shown in SEQ ID NO:21-24 may be also encoded due to the degenerated genetic code by otherpolynucleotides as well.

Moreover, the term “polynucleotide” as used in accordance with thepresent invention further encompasses variants of the aforementionedspecific polynucleotides. The polynucleotide variants, preferably,comprise a nucleic acid sequence characterized in that the sequence canbe derived from the aforementioned specific nucleic acid sequences shownin SEQ ID NO: 21-24 by at least one nucleotide substitution, additionand/or deletion whereby the variant nucleic acid sequence shall stillencode a polypeptide comprising the activities as specified above.Variants include polynucleotides comprising nucleic acid sequences whichare at least 70%, at least 75%, at least 80%, at least 85%, at least90%, at least 95%, at least 98% or at least 99% identical to the nucleicacid sequences shown in SEQ ID NO: 21-24. Moreover, also encompassed arepolynucleotides which comprise nucleic acid sequences encoding aminoacid sequences which are at least 70%, at least 75%, at least 80%, atleast 85%, at least 90%, at least 95%, at least 98% or at least 99%identical to the amino acid sequences shown in SEQ ID NO: 33-36. Thepercent identity values are, preferably, calculated over the entireamino acid or nucleic acid sequence region. A series of programs basedon a variety of algorithms is available to the skilled worker forcomparing different sequences. In this context, the algorithms ofNeedleman and Wunsch or Smith and Waterman give particularly reliableresults. To carry out the sequence alignments, the program PileUp (J.Mol. Evolution., 25, 351-360, 1987, Higgins et al., CABIOS, 5 1989:151-153) or the programs Gap and BestFit [Needleman and Wunsch (J. Mol.Biol. 48; 443-453 (1970)) and Smith and Waterman (Adv. Appl. Math. 2;482-489 (1981))], which are part of the GCG software packet [GeneticsComputer Group, 575 Science Drive, Madison, Wis., USA 53711 (1991)], areto be used. The sequence identity values recited above in percent (%)are to be determined, preferably, using the program GAP over the entiresequence region with the following settings: Gap Weight: 50, LengthWeight: 3, Average Match: 10.000 and Average Mismatch: 0.000, which,unless otherwise specified, shall always be used as standard settingsfor sequence alignments.

A polynucleotide comprising a fragment of any of the aforementionednucleic acid sequences is also encompassed as a polynucleotide of thepresent invention. The fragment shall encode a polypeptide which stillhas the activity as specified above. Accordingly, the polypeptide maycomprise or consist of the peptides of the present invention conferringthe said biological activities. A fragment as meant herein, preferably,comprises at least 50, at least 100, at least 250 or at least 500consecutive nucleotides of the aforementioned nucleic acid sequence orencodes an amino acid sequence comprising at least 20, at least 30, atleast 50, at least 80, at least 100 or at least 150 consecutive aminoacids of the aforementioned amino acid sequence.

The polynucleotides of the present invention either essentially consistof the aforementioned nucleic acid sequences or comprise theaforementioned nucleic acid sequences. Thus, they may contain furthernucleic acid sequences as well. Specifically, the polynucleotides of thepresent invention may encode fusion proteins wherein one partner of thefusion protein is a polypeptide being encoded by a nucleic acid sequencerecited above. Such fusion proteins may comprise as additional partother polypeptides for monitoring expression (e.g., green, yellow, blueor red fluorescent proteins, alkaline phosphatase and the like) or socalled “tags” which may serve as a detectable marker or as an auxiliarymeasure for purification purposes. Tags for the different purposes arewell known in the art and comprise FLAG-tags, 6-histidine-tags, MYC-tagsand the like.

The polynucleotide of the present invention shall be provided,preferably, either as an isolated polynucleotide (i.e. isolated from itsnatural context) or in genetically modified form. The polynucleotide,preferably, is DNA including cDNA or RNA. The term encompasses single aswell as double stranded polynucleotides. Moreover, comprised are alsochemically modified polynucleotides including naturally occurringmodified polynucleotides such as glycosylated or methylatedpolynucleotides or artificial modified one such as biotinylatedpolynucleotides.

The present invention further relates to a vector comprising thepolynucleotide of the present invention.

The term “vector”, preferably, encompasses phage, plasmid, viral orretroviral vectors as well as artificial chromosomes, such as bacterialor yeast artificial chromosomes. Moreover, the term also relates totargeting constructs which allow for random or site-directed integrationof the targeting construct into genomic DNA. Such target constructs,preferably, comprise DNA of sufficient length for either homologous orheterologous recombination as described in detail below. The vectorencompassing the polynucleotides of the present invention, preferably,further comprises selectable markers for propagation and/or selection ina host. The vector may be incorporated into a host cell by varioustechniques well known in the art. For example, a plasmid vector can beintroduced in a precipitate such as a calcium phosphate precipitate orrubidium chloride precipitate, or in a complex with a charged lipid orin carbon-based clusters, such as fullerens. Alternatively, a plasmidvector may be introduced by heat shock or electroporation techniques.Should the vector be a virus, it may be packaged in vitro using anappropriate packaging cell line prior to application to host cells.Retroviral vectors may be replication competent or replicationdefective. In the latter case, viral propagation generally will occuronly in complementing host/cells.

More preferably, in the vector of the invention the polynucleotide isoperatively linked to expression control sequences allowing expressionin prokaryotic or eukaryotic cells or isolated fractions thereof.Expression of said polynucleotide comprises transcription of thepolynucleotide, preferably into a translatable mRNA. Regulatory elementsensuring expression in eukaryotic cells, preferably mammalian cells, arewell known in the art. They, preferably, comprise regulatory sequencesensuring initiation of transcription and, optionally, poly-A signalsensuring termination of transcription and stabilization of thetranscript. Additional regulatory elements may include transcriptionalas well as translational enhancers. Possible regulatory elementspermitting expression in prokaryotic host cells comprise, e.g., the lac,trp or tac promoter in E. coli, and examples for regulatory elementspermitting expression in eukaryotic host cells are the AOX1 or GAL1promoter in yeast or the CMV-, SV40-, RSV-promoter (Rous sarcoma virus),CMV-enhancer, SV40-enhancer or a globin intron in mammalian and otheranimal cells. Moreover, inducible expression control sequences may beused in an expression vector encompassed by the present invention. Suchinducible vectors may comprise tet or lac operator sequences orsequences inducible by heat shock or other environmental factors.Suitable expression control sequences are well known in the art. Besideelements which are responsible for the initiation of transcription suchregulatory elements may also comprise transcription termination signals,such as the SV40-poly-A site or the tk-poly-A site, downstream of thepolynucleotide. In this context, suitable expression vectors are knownin the art such as Okayama-Berg cDNA expression vector pcDV1(Pharmacia), pBluescript (Stratagene), pCDM8, pRc/CMV, pcDNA1, pcDNA3(InVitrogene) or pSPORT1 (GIBCO BRL). Preferably, said vector is anexpression vector and a gene transfer or targeting vector. Expressionvectors derived from viruses such as retroviruses, vaccinia virus,adeno-associated virus, herpes viruses, or bovine papilloma virus, maybe used for delivery of the polynucleotides or vector of the inventioninto targeted cell population. Methods which are well known to thoseskilled in the art can be used to construct recombinant viral vectors;see, for example, the techniques described in Sambrook, MolecularCloning A Laboratory Manual, Cold Spring Harbor Laboratory (1989) N.Y.and Ausubel, Current Protocols in Molecular Biology, Green PublishingAssociates and Wiley Interscience, N.Y. (1994).

Preferably, the vector is a vector mediating expression of thepolynucleotide of the present invention in a host cell. The skilledartisan knows how to select combinations of vectors and host cells forpropagation of a vector and/or for expression of a protein encoded bythe vector.

Furthermore, the present invention relates to a host cell comprising thepolynucleotide or the vector of the present invention.

A “host cell”, as used herein, relates to a bacterial, archaeal, oreukaryotic cell with the capacity to propagate the vector of the presentinvention and I or to produce a polypeptide encoded on the vector or thepolynucleotide of the invention. Preferably, the host cell is abacterial cell from the species Escherichia coli, a lepidopteran, amouse, rat, or a human cell. Preferably, the host cell is a cellcultivated in vitro, more preferably a 293HEK cell. Also preferably, thehost cell is an APC, more preferably a B-cell, most preferably anactivated B-cell from a lymph node, a lymphoblastoid cell, a restingB-cell, or a neoplastic B cell, e.g. from a lymphoma.

The present invention contemplates a method for the stimulation ofantigen-specific T-cells, comprising a) contacting antigen presentingcells (APC) with a polypeptide, the polynucleotide, or the vector of thepresent invention, b) contacting said APC with T-cells, and c) therebystimulating antigen-specific T-cells specific for said at least oneT-cell epitope.

The method of the present invention, preferably, is an in vitro method.Moreover, it may comprise steps in addition to those explicitlymentioned above. For example, further steps may relate, e.g., toisolating the antigen presenting cells (APC) for step a), or inclusionof T-cell stimulatory agents in step b).

The term “antigen”, as used herein, relates to the protein chosen as thesource of the T-cell epitope of the present invention. The term “antigenspecific T-cells” relates to T-cells presenting on their surface T-cellreceptor molecules specifically recognizing, i.e. binding to, the T-cellepitope of the present invention presented in the context of an MHCmolecule. Preferably, the MHC molecule is an MHC class II molecule;thus, preferably, the T-cell is a CD4+ T-cell.

The term “contacting” as used in the context of the methods of thepresent invention is understood by the skilled person. Preferably, theterm relates to bringing a polypeptide, a polynucleotide, a vector, or acell of the present invention in physical contact with a subject or,preferably, a cell, i.e. allowing the aforementioned components tointeract.

As used herein, the term “antigen presenting cell” or “APC” relates to aB-cell or a follicular dendritic cell expressing at least one of theBCRC proteins on its surface. Preferably, the APC is a B-cell, morepreferably an activated B-cell from a lymph node, a lymphoblastoid cell,a resting B-cell, or a neoplastic B cell, e.g. from a lymphoma.

Furthermore encompassed by the present invention is a method forimmunizing a subject against an infectious agent, comprising a)contacting said subject with a pool of polypeptides, polynucleotides, orvectors of the present invention, and b) thereby immunizing said subjectagainst an infectious agent.

As used herein, the term “pool of polypeptides” relates to a collectionof polypeptides according to the present invention comprising at leasttwo, at least three, at least four, at least five, at least ten, atleast 20, at least 50, at least 100 different immunogenic peptidesselected from a library of immunogenic peptides found in patients with along-standing infection with a specific infectious agent. The skilledartisan knows how to establish said library of immunogenic peptides(Reineke, U., et al. (2002) J. Immunol. Methods. 267(1):37-51;Milosevic, S., et al. (2006), J. Virol. 80(20:10357-10364;Pedroza-Roldan, C., et al. (2009), 47:270-282). The terms “pool ofpolynucleotides” and “pool of vectors” are to be understood mutatismutandis.

The present invention relates to a method for immunizing a subjectagainst B-cell hyperproliferation, comprising a) contacting said subjectwith a polypeptide comprising a strong T-cell epitope as an immunogenicpeptide, with a polynucleotide of the present invention comprising asequence encoding a strong T-cell epitope, or with a vector of thepresent invention comprising a sequence encoding a strong T-cellepitope, and b) thereby immunizing said subject against B-cellhyperproliferation.

The term “strong T-cell epitope” relates to a T-cell epitope for whichthe probability that T-cells recognizing said T-cell epitope are presentin a subject is high. Preferably, T-cells recognizing the strong T-cellepitope are present at a high frequency in a subject. Preferably, theT-cell epitopes are selected from the proteins of viruses commonlyinfecting said subject, or against which said subject has beenvaccinated. More preferably, the strong T-cell epitopes are selectedfrom viral proteins used for immunization. Most preferred strong T-cellepitopes are, for example, from EBV latent antigens such as the EBNA-3C3H10 peptide (VVRMFMRERQLPQS, SEQ ID NO: 43).

The present invention also relates to a method for inducing tolerance ina subject, comprising a) contacting said subject with atolerance-inducing polypeptide, with a polynucleotide encoding atolerance-inducing polypeptide, or with a vector encoding atolerance-inducing polypeptide, and b) thereby inducing tolerance in asubject.

The term “tolerance-inducing polypeptide”, as used herein, relates to apolypeptide of the present invention inducing a decreased response to animmunogenic peptide in a subject. Preferably, the tolerance-inducingpolypeptide comprises a binding peptide recognizing CD22 as a bindingpeptide, more preferably, the tolerance-inducing polypeptide is ananti-CD22 antibody fused to an immunogenic peptide.

All references cited in this specification are herewith incorporated byreference with respect to their entire disclosure content and thedisclosure content specifically mentioned in this specification.

Figure Legends:

FIG. 1: T cell assay performed with EBV-transformed B cells (LCLs) usedas antigen-presenting cells, pulsed with various amounts of antibodiesfused with the 5H11 epitope from the EBV EBNA3C protein or with theirrespective heavy chain (HC). Antibodies tested are specific for CD21,CD19 and CD22. Positive controls include cells incubated with 5H11peptide epitope, negative controls include anti-CD19, anti-CD21 oranti-CD22 antibodies devoid of antigens. Results are given in picogramsIFN-gamma per ml.

FIG. 2: T cell assay performed either with EBV-transformed B cells(LCLs) or the Burkitt's lymphoma cell line AG876 used asantigen-presenting cells, and pulsed with various amounts ofCD21-specific antibodies fused with the 3H10 epitope from the EBV EBNA3Cprotein. Positive controls include cells incubated with 3H10 peptideepitope, negative controls anti-CD21 antibodies devoid of 3H10 or 3H10anti-CD21 fusion proteins devoid of light chain. Results are given inpicograms IFN-gamma per ml.

FIG. 3: Treatment of EBV-transformed B cells (LCLs) and Burkitt'sLymphoma cell lines with polypeptides according to the inventioncomprising EBNA3C-3H10 leads to antigen presentation and efficient Tcell activation. B cells were treated for 24 h with 1 ng B-cell targetedantibodies (αCD-21, -20, -19, and -22) loaded with EBNA3C epitope.Positive controls included cells pulsed with increasing amounts (1 ng-1mg) of 3H10 peptide alone, and negative controls included eitheruntreated cells, or cells pulsed with antibodies not containing theEBNA3C-3H10 epitope. Following treatment, B cells were mixed withEBN3C-3H10-specific T cell clones at a ratio of 1:2. After 24 h,secretion of IFNγ was measured by ELISA as an indicator of T cellactivation. Results are given in pg/ml.

FIG. 4: Antigen presentation by polypeptides according to the inventioncomprising EBNA3C-3H10 results in peptide-specific cell killing by CD4+T cells. LCLs were treated with EBNA3C-3H10-loaded αCD19 antibody(CD19-3H10 Ab; 1 ng and 10 ng), αCD19 antibody containing no epitope(CD19 Ab), or EBNA3C peptide, or were left untreated. These target cellswere then labeled with ⁵¹Cr and co-incubated for 4 h withEBNA3C-3H10-specific effector T cells at an increasing effector:targetratio (1:1, 3:1, 6:1, 12:1, 25:1, 50:1). A ⁵¹Cr-release assay wasperformed to determine the % lysis of the target LCL population as ameasure of specific cell killing.

FIG. 5: General schedule of MCMV infection, lymphoma cell delivery andantibody treatment for mouse experiments of Example 5.

The following Examples shall merely illustrate the invention. They shallnot be construed, whatsoever, to limit the scope of the invention.

EXAMPLE 1

Antibodies against CD21, CD19 and CD22 were fused with an antigenicepitope (5H11) from the Epstein-Barr virus latent antigen EBNA3C. Thefusion proteins were used to introduce the epitope into the endosome ofB cells transformed by the Epstein-Barr virus (lymphoblastoid celllines, LCLs). The pulsed B cells were then co-cultured with a T cellclone that is specific for the EBNA3C 5H11 epitope. T cell activationwas assessed by measuring interferon-γ release in the supernatant.

LCLs directly incubated with the 5H11 epitope were used as positivecontrols. Antibody-5H11 fusion proteins devoid of light chains were usedas negative controls, as were antibodies not fused with the epitopes.

1 ng of CD21-5H11 fusion proteins which carry 20 pg of 5H11 elicited animmune response comparable to the one obtained with 1 μg of peptide(FIG. 1). Therefore, the efficiency of antigen presentation on activatedB cells was 50.000 times higher after fusion with CD21 antibody thanwith the epitope alone. Similar results were obtained with the CD 19,CD20, and CD22-specific antibodies. It is important to note thatuntreated EBV immortalized B cells cannot present 5H11 on the class IIpathway.

EXAMPLE 2

LCLs and AG876, a Burkitt's lymphoma cell line, were used asantigen-presenting B cells and their respective abilities to present the3H10 epitope from the EBNA3C protein fused to CD21-specific antibodieswas determined by an interferon-γ release assay. 3H10 peptides aloneprovided a positive control, non-functional fusion proteins devoid ofheavy or light chains, mock-treated antigen-presenting cells were takenas negative controls.

Both LCLs and AG876 presented 3H10 epitopes with a similar efficiency(FIG. 2). The AG876 presented 3H10 after incubation with the CD21antibody-3H10 fusion protein less efficiently than LCLs but remainedapproximately 100 times more efficient than unconjugated 3H10. Thisrelative decreased efficiency is consistent with defective antigenprocessing machinery in Burkitt's lymphoma cells. Nevertheless, the CD21antibody-3H10 fusion protein elicited a potent immune response againstthe tumor cells.

EXAMPLE 2.1 Further Evaluating Polypeptides According to the Inventionin EBV-Transformed B Cells and Various Burkitt's Lymphoma Cells Lines

A panel of antibodies loaded with various EBV epitopes has beengenerated. These have been evaluated for their ability to presentantigen to peptide-specific T cells and to activate these T cells. InFIG. 3 is shown one example of treatment with a polypeptide according tothe invention comprising an epitope from the EBNA3C protein. We wereable to show that treatment with these polypeptides according to theinvention results in specific T cell activation in LCLs and in severalBurkitt's lymphoma cell lines.

EXAMPLE 2.2 Determining the Potential for T Cells Activated by Treatmentwith Polypeptides According to the Invention to Kill their Target Cells

Since polypeptides according to the invention can efficiently activatepeptide-specific T cells, we wanted to determine whether these activatedT cells are able to specifically kill the B cells presenting theepitopes from the immunogenic peptides. Here we performed ⁵¹Cr-releaseassays to demonstrate that the activated T cells can indeed kill theirtargets. FIG. 4 shows one example of this in LCLs.

EXAMPLE 2.3 In Vivo Studies in a Mouse Lymphoma Model

A panel of polypeptides according to the invention in the form of “armedantibodies” containing T cell epitopes from common mouse pathogens aregenerated. B cell surface receptors CD-19, -20, -21 and -22, aretargeted and the antibodies are coupled to the pp89 peptide, animmunodominant T cell epitope from the IE1 protein of mousecytomegalovirus (MCMV). These antibodies are studied in the A20 model ofmouse lymphoma. Injection of the A20 cell line into MCMV-positive BALB/cmice results in the development of disease that resembles human diffuselarge B cell lymphoma (DLBCL).

The serostatus of the animals to MCMV is assessed by serology prior tothe commencement of the study. Seronegative animals are infected withMCMV in order to ensure seroconversion and priming of T cells againstthe MCMV pp89 peptide. All animals are re-infected with the virus 4weeks prior to i.v. challenge with A20 lymphoma cells (FIG. 5). At days5 and 15 following lymphoma cell delivery, animals are treated with therecombinant AgAbs containing pp89 peptides. Mice are subsequentlymonitored for survival and tumour development for 120 days followinglymphoma cell challenge. Mice are sacrificed when external signs ofsuffering are present (such as reduced mobility and altered behaviour),as per the guidelines recommended by the Society of Laboratory AnimalScience (GV-SOLAS), or if no adverse symptoms appear, at 120 daysfollowing injection of cells. Refer to FIG. 5 for a schematicrepresentation of this experimental schedule.

Molecular resonance imaging (MRI) is used in order to monitor tumourdevelopment at two time-points during the course of the study. MRIallows to both visualize the tumours and to perform volumetric analysisof the tumours. Imaging of all mice is performed when signs of tumourdevelopment are evident in the untreated group, and again prior tosacrifice. In addition, anatomical and histological examinations areperformed upon sacrifice of the mice.

Using the experimental schedule outlined in FIG. 5, a panel ofantibodies and treatment regimes is investigated. Firstly, antibodiesagainst the full panel of B cell surface receptors, CD 19, -20, -21 and-22 are tested, using antibody and adjuvant (Poly I:C) co-treatment.Peptide-loaded and unloaded antibodies are compared in targeting thesesurface receptors. Tumour growth and animal survival are monitored asmarkers of treatment efficacy, and are compared relative to untreatedcontrol animals and animals without lymphoma. Further experimentsinclude: i) determination of the most effective dose of antibodytreatment; and ii) an evaluation of the efficacy of treatment with armedantibodies and CD20/rituximab co-injection. Indeed, antibodies directedagainst CD21 or CD19 have been found to evince low cytotoxic propertiesthat could be instead provided by anti-CD20 antibodies and thereforecombine two different angles of attack against the lymphoma cells.

Once a panel of antibodies has been tested in the A20 lymphoma model,studies are extended to other lymphoma models. This includes the BCL1model in which BCL1 cells can induce a DLBCL-like or CLL-like lymphoma,depending on the route of inoculation (i.p. or i.v, respectively), and aBurkitt's lymphoma-like model using cells from B6-myc transgenic mice.

EXAMPLE 3

Presentation of microbial antigens at the surface of B. lymphocyte cellselicits recognition and destruction through T cells specific to theseantigens. These T cells are present in most individuals who werepreviously infected by common viruses, such as herpesviruses.Individuals with a chronic Hepatitis C or HIV infection carry anincreased proportion of activated B cells that can efficiently presentantigens (Moir and Fauci, 2009, Nat Rev Immunol; Sugalski, Rodriguez,Moir, Anthony, 2010, J. Immunology). These infectious agents have anintrinsic ability to modify their surface antigens and subsequently theyare able to evolve faster than the host's immune system can adapt. As aresult, infected patients cannot clear their infections.

To overcome this problem, a library of polypeptides is generated,comprising anti-CD21 antibodies coupled to a library of Hepatitis Cantigens that are found in patients with a long-standing infection,which covers the spectrum of viral antigens that appear in the course ofinfection and include all stages of virus evolution. This antibodylibrary is administered to patients with a recently acquired Hepatitis Cand thus primes the patient's immune system against all possible virusvariants and therefore enables their elimination.

The same method is applied to patients recently infected with HIV, usinga library of HIV antigens that are found in patients with along-standing infection, which covers the spectrum of viral antigensthat appear in the course of infection and include all stages of virusevolution.

EXAMPLE 4

An antibody fusion protein is created, comprising an anti-CD21 antibodyfused to an immunodominant peptide from a common viral or bacterialpathogen, for example EBNA3C from EBV, and produced according toconventional methods. The antibody fusion proteins are administered topatients suffering from B-cell lymphoma, where they are taken up byLymphoma cells. The Lymphoma cells present the T-cell epitopes comprisedin the EBNA3C peptide and thus activate EBNA3C-specific T-cells, whichin turn eliminate the presenting Lymphoma cells. CD4+ T cells can alsoact as ‘cytotoxic’ T cells to orchestrate the killing of target cells.There is also the possibility of cross-presentation to CD8+ T cells.

EXAMPLE 5

An antibody fusion protein is created, comprising an anti-CD22 antibodyfused to myelin basic protein (MBP). The fusion protein is applied topatients at a high dose. Thus, tolerance to MBP is induced and thusprogression of Multiple Sclerosis is reduced.

1-25. (canceled)
 26. A polypeptide comprising: (a) a binding peptidebinding to at least one protein selected from the group consisting ofCD22, CD19, CD20, and CD21; and (b) an immunogenic peptide comprising atleast one T-cell epitope suitable for use in the modulation of theimmune response in a subject, preferably for use in vaccination of asubject against B-cell hyperproliferation.
 27. The polypeptide of claim26, wherein the binding peptide is an antibody.
 28. The polypeptide ofclaim 26, wherein the immunogenic peptide comprises: (a) at least oneT-cell epitope from a tumor antigen; and/or (b) at least one T-cellepitope selected from the proteins of viruses commonly infecting thesubject or against which the subject has been vaccinated.
 29. Thepolypeptide of claim 26, wherein the immunogenic peptide comprises atleast one T-cell epitope from a latent gene of Epstein-Barr Virus (EBV).30. The polypeptide of claim 26, wherein the modulation of the immuneresponse is an activation.
 31. The polypeptide of claim 26, wherein thebinding peptide is an antibody directed to CD21 or a peptide comprisingthe CD21-binding peptide of EBV gp350.
 32. The polypeptide of claim 26,wherein the modulation of the immune response is a repression.
 33. Thepolypeptide of claim 26, wherein the binding peptide is a single-chainantibody.
 34. The polypeptide of claim 26, wherein at least a part ofthe binding peptide is contiguous in amino acid sequence with theimmunogenic peptide or with an adapter binding the immunogenic peptide.35. A method for the stimulation of antigen-specific T-cells comprising:(a) contacting antigen presenting cells (APC) with a polypeptideaccording to claim 26; (b) contacting the APC with T-cells; and (c)thereby stimulating antigen-specific T-cells specific for the at leastone T-cell epitope.
 36. The method of claim 35, wherein the APC areB-cells.
 37. The method of claim 35, wherein the APC are lymphoblastoidcell lines (LCL).
 38. The method of claim 35, wherein the method is anin vitro method.
 39. A method for immunizing a subject against B-cellhyperproliferation comprising: (a) contacting the subject with apolypeptide according to claim 26, comprising a strong T-cell epitope asan immunogenic peptide; and (b) thereby immunizing the subject againstB-cell hyperproliferation.
 40. The method of claim 39, wherein thestrong T-cell epitope is a T-cell epitope selected from the proteins ofviruses commonly infecting the subject or against which the subject hasbeen vaccinated.
 41. The method of claim 39, wherein the strong T-cellepitope is a T-cell epitope selected from viral proteins used forimmunization.
 42. The method of claim 39, wherein B-cellhyperproliferation is infectious mononucleosis, post-transplantproliferative disease (PTLD), or B-cell lymphoma.
 43. A method forimmunizing a subject against an infectious agent comprising: (a)contacting the subject with a pool of polypeptides according to claim26; and (b) thereby immunizing the subject against an infectious agent.44. The method of claim 43, wherein the pool of polypeptides is acollection of polypeptides comprising at least two different immunogenicpeptides selected from a library of immunogenic peptides found inpatients with a long-standing infection with the infectious agent.